sorry, the title is a bit confusing, but what i’m curious to know is what those few locomotives that, in their names, have letters in them mean. take the SD60M for example. what does the M mean or represent? i know that the SD60M differs from the SD60 in that it has a widenose cab. so then wouldnt it be called an SD60W? what does the I mean? like in the SD70I? what does MAC mean?
also, why is the SD90 called the SD9043MAC? why did EMD go from the eighty to the nine thousand and forty three?
what i know so far-
M=?
I=Isolated
W=Widenose Cab
T=Tunnel Motor
Q=?
X=Experimental
R=?
L=?
The M in mac i dont know, but the AC is alternating current . The W is strictly a GE thing, besides the GP40-2LW (W isnt even supposed to be in the name, railfans just added it, or so im told) only GE units have the W. Oh yes the SD70I and SD60I , the I is for Isolated. The SD90Macs are around, but most are the SD9043Macs, meaning it has 4,300 HP.
M is for widecab, I think it stems from Modified North American cab.
L also means widecab (At least on CN’s GP40-2s like Alex mentioned above)
I think the reason EMD went straight from 80 to 90 is due to the fact that the SD80s had 20 cylinder blocks and the 90s had the usual 16. There are two types of SD90: The SD90/43MAC and the SD90MAC-H. The latter was the only planned SD90, with a 6000hp H block. There were problems in the development of a 6000hp engine for both GE and EMD, and both temporarily offered ‘upgradeables’, locomotives with a lower horsepower that could be upgraded to 6000HP once the prme mover was availible. GE used its existing AC4400CW design, while EMD made the 4300HP SD90/43MAC, hence the 43 in the name.
R is probably for rebuilt, seeing as CN’s rebuilt geeps are GP9Rs.
BTW, if you ever come across a CP SW1200RSu, RS=Road switcher (higher gearing and different trucks) and u is for upgraded, like on their GP9s.
Because EMD didn’t assign them that designation - that’s a designation assigned by the railroad that owned and/or rebuilt the units.
Here’s the latest version of my opus on diesel nomenclature. This document is regularly updated. I welcome any and all corrections, clarifications or feedback.
I have only covered builders’ designations here - there are variations by rebuilders and railroads that differ from the pattern shown, as well as exceptions within builder nomenclatures. General Electric, for instance, uses at least two different and equally-valid nomenclature sequences.
xx: Type
DD = 8-axle freight locomotive.
E = 6-axle passenger locomotive with A1A (3 axles, center axle unpowered) trucks.
F = 4 or 6-axle cowl-body freight or passenger locomotive. May include steam generator or HEP equipment (see PH suffix below for an explanation of HEP).
FP = 4 or 6-axle cowl-body passenger locomotive with steam generator.
GP = 4-axle hood-type road switcher.
SC = 4-axle switcher, cast frame.*
SD = 6-axle road switcher.
SDP = 4-axle road switcher equipped with steam generator.
SW = 4-axle switcher, welded frame.*
TR = 4-axle switcher with permanently-coupled 4-axle booster.
On early EMD switchers “S” and “N” denoted “Six” and “Nine” hundred horsepower. This was later dropped and welded frames became the standard; from the SW7 on, “SW” denoted a 4-axle switcher.
yy: Series
7,9,40, etc.- No direct correlation to horsepower
Common Suffixes:
A = Cowl-body unit equipped with cab (e.g. F7A)
Post-1985: Cowl-body unit with next-generation prime m
The DL535 is an Alco export design, with model RSD30/RSD35. The following link will explain EMD export models: http://emdexport.railfan.net/frame_layout.html
GE export models have similar designations to domestic designs.
FM also had a specification number, the ALT series, that was similar to Alco’s DL designations. For example, the Erie-builts had spec numbers ALT100.3 and ALT200.3, the H10-44 was ALT100.6A, etc.
A=Cab equipt. unit or it could mean special order(longer frame, usually for bigger fuel tank)
AC=alternator rectifier on older (2nd gen) units or on newer units AC traction motors
B=Cabless unit (may have a de-commisioned cab)
D=duty as in SD special duty or DD double duty
E=on earlier streamliners-eighteen hundred HP (6axle A-1-A)
E=at the end-EMD rebuild
e=Tier 2 emmisions compliant
F=on earlier streamliners-fourteen hundred HP (4axle)
F=on later units-full body (cowl unit)
GP=general purpose (4axle)
H=head end power equipt on passenger units
H=4 stroke cycle H series prime mover on freight units
I=isolated “whisper cab”
L=lightweight (may have 3axle A-1-A trucks)
M=north american safty cab or wide cab (without an AC after it implies DC
M=Morrison Knudsen rebuilt unit
MP=multi purpose (4axle switchers)
N=nine hundred HP on earlier switchers
P=passenger unit
R=rebuild
S=six hundred HP on earlier switchers
SD=Special Duty (6-axle)
T=twelve hundred HP on earlier switchers units
T=tunnel motors on SD40s & SD45s
u=rebuilt units in canada
V=VMV re built unit
W=wide cabs in Canada (not sure on this one)
X=experimental unit
-2=modular electrical cabinet
-3=advanced electronics / traction controll
whoa, thanks guys. that pretty much sums up everything i wanted to know. not sure why M means widenose on EMD and W is widenose for GE. seems like the letters should be universal. oh well.
It must be a railroad thing too, since CN referred to those engines as GF-430s and as GP40-2LWs.
The W suffix is also applied to other EMD products and to the M420Ws; since the latter were from a different builder altogether, and since the “W” cabs on EMD and MLW products were built to CN specifications (versus the GE version, which was not), it stands to reason that this is at the least a CN designation.
Canadian railroads (At least) had their own standardized designation for every engine, but CN’s was more complicated than CP’s. It was easier than using the builder’s designations, but the easiest was CP’s. I’m pretty sure that they weren’t used as much as the builder’s designations, tho. CN’s went like this:
First letter: E = GE, G = GMD/EMD, M = ALCo/MLW
Second letter. This is the type of unit. F = road freight, H = hump unit, P = Passenger, R = Road switcher, S = switcher, and Y = yard. Don’t ask me exactly what those mean…
Third letter (not always there) A = A unit rather than B, G = Equipped with steam generator, L = Leading unit of a hump set, and T = trailing unit of a hump set.
CP’s was easier, and is as follows:
Letters: DS = Diesel switcher (ie SW1200), DRS = Diesel road switcher (ie GP38-2, maybe SD40s, can’t remember) and DRF = Diesel road freight (ie AC4400 and SD90). The next numbers are the hp/100.
Of course, don’t let yourself get confused by these…
I am new hear. Looking for info on truck foward. New York Central had them in the 1950s. I was lucky to have spend the day in the cab. Did alot oftaking the trains around the loop.the smell was of burnt oil and i was about 9 at the time. Think they were the p1
and p2s. Can they still be around . Live in NJ
Isolated means the cab sits on big bushings and is “isolated” from the rest of the body. They are also called whisper cabs. They are suppose to isolate noise from the rest of the unit from the cab.